Acid gas treatment

ABSTRACT

Apparatus and methods for treating acid gas, which utilizes multi-stage absorption cycle of ammonia desulfurization to treat acid tail gas after pre-treatment of the acid gas, thereby achieving the purpose of efficient and low-cost treatment of acid tail gas. The parameters of the acid tail gas may be adjusted by a regulatory system such that the enthalpy value of the acid tail gas is in the range of 60-850 kJ/kg dry gas, for example, 80-680 kJ/kg dry gas or 100-450 kJ/kg dry gas, to meet the requirements of ammonia desulfurization, and achieve the synergy between the acid gas pre-treatment and ammonia desulfurization. Furthermore, hydrogen sulfide may be converted into sulfur/sulfuric acid plus ammonium sulfate at an adjustable ratio.

This application claims priority under 35 U.S.C. § 119 of Chinese PatentApplication No. Application No. 201810804898.6, filed on Jul. 20, 2018,which is hereby incorporated herein in its entirety.

TECHNICAL FIELD

The disclosure relates to removing acidic sulfide gas (such as hydrogensulfide, sulfur dioxide, COS, CS₂, etc.) in production processes ofpetrochemical, natural gas chemical, coal chemical industries and otherindustries by utilizing an ammonia desulfurization process. Thedisclosure specifically relates to treating acid gas, wherein an ammoniadesulfurization process is used to treat the acid tail gas, therebyachieving the purpose that net tail gas meets the discharge standardsthrough multi-stage circulating absorption, in particular, wherein theenthalpy value of the acid tail gas is first adjusted by a regulatorysystem, and then the acid tail gas is fed into a subsequent ammoniadesulfurization process. The disclosure further relates to acorresponding device for treating acid gas, which may be applied to thetechnical fields of petrochemical, natural gas chemical, coal chemicalindustries and the like.

BACKGROUND

Acid gas refers to the process gas that includes, among other things,sulfur-containing materials such as hydrogen sulfide, sulfur oxides,organic sulfur and the like, which is derived from petrochemical,natural gas chemical, coal chemical, shale oil chemical, and shale gaschemical industries and the like. The harmful components in the acid gasare primarily hydrogen sulfide, sulfur dioxide, COS, CS₂, etc. with ahigh concentration of H₂S (generally, 70%-95% for petrochemicalindustry, 30%-80% for natural gas chemical industry, and 20%-50% forcoal chemical industry), and need to be treated to meet a dischargestandard.

There are various methods for treatment technologies ofsulfide-containing acid gas, such as conventional Claus plushydrogenation reduction absorption regeneration (low temperature SCOT)technology, dry process for making sulfuric acid, incineration plus tailgas desulfurization technology, wet process for making sulfuric acid,conventional Claus plus Super(Euro)Claus technology, conventional Clausplus tail gas incineration plus tail gas desulfurization technology,conventional Claus plus catalytic oxidation, conventional Claus plusbiological desulfurization, etc., wherein the most commonly usedtechnology is the conventional Claus plus hydrogenation reductionabsorption regeneration technology.

In the Claus sulfur recovery stage, 85%-99% of hydrogen sulfide isconverted into sulfur, and less than 15% of the sulfide is reduced byhydrogenation, absorbed and regenerated to obtain H₂S which is returnedto the Claus sulfur recovery device.

However, after the above treatments, the acid gas is still difficult tomeet environmental standards and cannot be directly discharged, andfurther treatment is required. Further treatment technologies includetail gas desulfurization by alkali method, tail gas bio-desulfurization,Cansolv and the like. With increasingly strict standards for sulfurdischarged into the environment, a compulsory sulfur recovery rate mayreach 99.9% or more, and the sulfur oxide concentration in the tail gasmay be required to be controlled at 100 mg/Nm³ or even below 50 mg/Nm³.

However, in general, existing processes have large investment, highoperating cost, and high emission concentrations of pollutants, or evenhave difficulty in meeting discharge standards, especially during thestartup and shutdown periods.

The Chinese invention patent with Application No. CN 200910188118discloses a high-concentration flue gas desulfurization method, whichuses sodium-method desulfurization and simultaneously recovers theby-product sodium sulfite, wherein the flue gas is deoxidized beforedesulfurization. The concentration of sulfur dioxide in flue gas beforetreatment ranges between 10,000-100,000 mg/m³, the oxygen content rangesbetween 2,000-10,000 mg/m³, and the concentration of sulfur dioxide inthe flue gas after treatment is less than 200 mg/m³. Compared with thecommon sodium sulfite method, deoxidation step in this method requiresconversion of part of sulfur dioxide into low-value low-concentrationsulfuric acid as an efflux, and the recovery rate of sulfur dioxide inthe flue gas is reduced. Furthermore, this method is difficult todeoxidize thoroughly, the purity of the product sodium sulfite is low,and this method has large investment and high operating cost.

The Chinese invention patent with Application No. CN 200580011908.Xdiscloses a biological desulfurization technology, which is used forbiological desulfurization of Claus tail gas to obtain desulfurized tailgas and sulfur product. The main process is that: tail gas is introducedinto an absorber and contacted with a lean solvent to obtaindesulfurized tail gas and a rich solvent; the rich solvent is introducedinto a bioreactor device in which the dissolved hydrogen sulfide isbio-oxidized to obtain a sulfur product and a lean solvent. The hydrogensulfide in the tail gas can be less than 10 ppm. This method has largeinvestment, difficult operation, and waste liquid discharge, and it isdifficult to keep the continuous and stable biological activity.

The Chinese invention patent with Application No. U.S. Pat. No.5,019,361 illustrates the Cansolv process flow as below: theconcentration of sulfur dioxide is 7×10⁻⁴-5×10⁻³, the mass concentrationof the organic amine liquid is not less than 20%, the temperature ofabsorption liquid is 10° C.-50° C., sulfur dioxide absorbed per 1,000 gof absorption liquid is greater than 100 g, the desorption temperatureis 70° C.-90° C., and 4 g-10 g of steam will be consumed per desorptionof 1 g of sulfur dioxide. This method has large investment, waste aciddischarge and high energy consumption.

The Chinese invention patent with Application No. CN 201210288895discloses a method for treating Claus process tail gas, in which theClaus process tail gas containing sulfur dioxide, oxygen and water iscontinuously added into a reactor filled with a porous carbondesulfurizer; at a reaction temperature of 30° C.-150° C., sulfurdioxide and water in the tail gas undergo catalytic oxidation reactionon the surface of the porous carbon to form sulfuric acid, and theregeneration detergent is continuously introduced into the reactor atthe same time. In this method, the desulfurization rate is up to 93%,and the final tail gas discharge cannot meet the high environmentalprotection requirements, and the by-product low-concentration sulfuricacid is difficult to use. The multi-stage Claus process tail gas stillfails to meet the discharge requirements.

Countries around the world discharge sulfur dioxide to differentdegrees. China's sulfur dioxide emissions are huge and have a greatimpact on the environment and society. The total amount of sulfurdioxide emissions in 2014 was 19.74 million tons, and the total amountof sulfur dioxide emissions in 2015 was 18.591 million tons, rankingfirst in the world, which caused a huge economic loss and seriouslyaffected China's ecological environment and people's health.

In view of the shortcomings of the above technologies and the reality ofsulfur dioxide emission load in China, various tail gas desulfurizationtechnologies are emerging. At present, there are hundreds of maturedesulfurization technologies, among which the wet desulfurizationprocess is the most widely used, accounting for about 85% of the world'stotal installed capacity of desulfurization. Common wet flue gasdesulfurization technologies include limestone-gypsum method, doublealkali-method, sodium carbonate-method, ammonia-method, magnesiumoxide-method, and the like. Ammonia desulfurization is a wetdesulfurization process using ammonia as an absorbent, this method canproduce ammonium sulfate fertilizer using SO₂, and is a green flue gasmanagement scheme with low energy consumption, high additional value andthe implementation of recycling utilization of resources. Since a largeamount of available ammonia water is generated in the production processof the chemical industry, the use of ammonia desulfurization may bedesirable for the tail gas in the chemical industry.

The ammonia desulfurization process is mainly composed of threeprocesses: absorption, oxidation and concentration (crystallization).Firstly, sulfur dioxide is absorbed with ammonium sulfite to obtain amixed solution of ammonium sulfite and ammonium hydrogen sulfite, andthen neutralization by adding ammonia is performed to obtain ammoniumsulfite again:

(NH₄)₂SO₃+H₂O+SO₂=2NH₄HSO₃

(NH₄)_(X)H(2-x)SO₃+(2-x)NH₃═(NH₄)₂SO₃

Oxidized air is introduced into the solution to oxidize ammonium(hydrogen) sulfite to obtain ammonium (hydrogen) sulfate:

(NH₄)₂SO₃+½O₂═(NH₄)₂SO₄

The circulating absorption liquid containing ammonium sulfate issubjected to concentration, crystallization, solid-liquid separation anddrying to obtain the final product, ammonium sulfate.

The Chinese invention patent with Application No. CN 201310130225.4discloses an ammonia-method flue gas management apparatus and methodsfor acid tail gas, specifically comprising the following steps: 1)controlling the concentration of sulfur dioxide in the tail gas to beintroduced into an absorption tower at ≤30000 mg/Nm³; 2) process wateror ammonium sulfate solution is provided in the inlet flue pipe of theabsorption tower or within the absorption tower for spraying to lowerthe temperature; 3) an oxidation section is provided in the absorptiontower, and an oxidation distributor is provided in the oxidation sectionto realize oxidation of the desulfurization absorption liquid; 4) anabsorption section is provided in the absorption tower, and anabsorption liquid distributor is used to achieve desulfurization sprayabsorption by the ammonia-containing absorption liquid in the absorptionsection; the ammonia-containing absorption liquid is supplementedthrough an ammonia storage tank; 5) the upper part of the absorptionsection in the absorption tower is equipped with a water washing layer,which washes the absorption liquid in the tail gas to reduce the escapeof the absorption liquid; 6) the upper part of the water washing layerin the absorption tower is equipped with a defogger to control thecontent of fog drops in the purified tail gas; in the coal chemicalindustry, the use of integrated desulfurization technology of Claussulfur recovery plus ammonia desulfurization can reduce the investmentcost of post-treatment, and the flow is simpler, and the process ismainly applied to acid gas treatment in the coal chemical industry,wherein the concentration of sulfur dioxide in the tail gas to beintroduced into the absorption tower needs to be controlled at ≤30,000mg/Nm³, and the requirements for other parameters of the tail gas suchas enthalpy value and impurity content are not specified.

The Chinese invention patent with Application No. CN 201410006886.0discloses a method for efficiently removing acidic sulfide gas usingammonia desulfurization technology, comprising the following steps: 1)pre-treatment: sulfide in acid gas is subjected to the pre-treatmentmethod such as sulfur recovery, sulfuric acid production and/orincineration, and thus the remaining sulfur in the acid gas is convertedinto sulfur oxides to obtain acid tail gas containing sulfur oxides; theacid gas is derived from petrochemical, natural gas chemical, coalchemical industries and the like; 2) ammonia absorption of sulfur oxide:the acid tail gas containing sulfur oxides is introduced into an ammoniaabsorption device, and the sulfur oxides are absorbed by a circulatingabsorption liquid; 3) ammonium sulfate post-treatment: the saturated ornearly saturated absorption liquid which fully absorbs sulfur oxides issubjected to concentration, crystallization, solid-liquid separation,and drying to obtain a solid ammonium sulfate product. Sulfur oxides(sulfur dioxide, sulfur trioxide, and hydrates thereof) are removed fromthe acid tail gas; furthermore, sulfuric acid, sulfur and ammoniumsulfate by-products are generated, and clean gas is discharged meetingthe standard. The components, density, circulation amount or otherparameters of the absorption liquid are adjusted according to differentsulfur oxide concentrations and sulfur oxide absorption amounts in theacid tail gas. When the concentration of sulfur oxide in the acid gas islower than 30,000 mg/Nm³, the acid gas is directly introduced into theammonia absorption device without pre-treatment. The enthalpy value andthe impurity content of the acid tail gas after the pre-treatment arenot specified in this process, as well as the treatment measures afterthe impurities enter the ammonia desulfurization system.

The Chinese patent applications with Application Nos. CN 201611185413.7,CN 201611185413.7, and CN 201810062243.6 have also attempted to improvethe treatment of acid tail gas by ammonia desulfurization, respectively,but these improvement measures are still not ideal. Moreover, thecontrol over the enthalpy value of the acid tail gas has not been notedin these publications either.

Therefore, it is desirable to determine more suitable acid tail gasparameters and further improve the desulfurization method. This mayreduce the investment and operating cost of the ammonia desulfurizationdevice, may achieve long-period stable operation, may achievesynergistic control of acid gas pre-treatment and ammoniadesulfurization of tail gas, may improve ammonia recovery rate, maycontrol the production of aerosol, and may improve the product quality.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and advantages of the invention will be apparent uponconsideration of the following detailed description, taken inconjunction with the accompanying drawings, in which like referencecharacters refer to like parts throughout, and in which:

FIG. 1 shows illustrative apparatus of Example 1 in accordance withprinciples of the invention.

FIG. 2 shows illustrative apparatus of Example 2 in accordance withprinciples of the invention.

FIG. 3 shows illustrative apparatus of a regulatory system in accordancewith principles of the invention.

LIST OF REFERENCE SIGNS

-   -   1. Acid gas    -   2. Sulfur recovery system    -   3. Sulfur/sulfuric acid    -   4. Sulfur-recovered tail gas    -   5. Incineration system    -   6. Acid tail gas    -   7. Regulatory system    -   8. Adjusted tail gas    -   9. Ammonia    -   10. Ammonia desulfurization system    -   11. Ammonium sulfate    -   12. Net tail gas    -   13. Sulfuric acid production system    -   14. Cooling apparatus    -   15. Dehumidifying apparatus    -   16. Sulfur removal device    -   17. Dust removal/impurity removal apparatus.

DETAILED DESCRIPTION Definitions

“Ammonia recovery” means that fraction or percentage of ammonia added toa gas cleaning process that is subsequently captured and extracted fromthe process.

“Dust” means a particulate material fine enough to waft along gaseousflows, when handled, processed, or contacted. It includes but is notlimited to aerosols, including solid aerosol particles and liquidaerosol particles, soot, charcoal, non-combusted coal, fine minerals,sand, gravel, salts, and any combination thereof.

“Oxidation rate” means the percentage, calculated by mol percent, of agiven material that has been converted into an identified more-oxidizedspecies of the material. For example, in a mixture containing ammoniabearing species and sulfur oxides, if X mol % of the mixture is ammoniumsulfate, Y mol % is ammonium sulfite, and Z mol % is some other ammonia,sulfur, and/or oxygen containing species with an oxidation potentialgreater than ammonium sulfate, because ammonium sulfate is theidentified most-oxidized species, the oxidation rate of the mixturewould be X mol %.

“Sulfur oxides or SOx” means a chemical species containing sulfur andoxygen. It includes compounds such as sulfur monoxide (SO), sulfurdioxide (SO₂), sulfur trioxide (SO₃), higher sulfur oxides (SO₃ and SO₄and polymeric condensates of them), disulfur monoxide (S₂O), disulfurdioxide (S₂O₂), and lower sulfur oxides (S₇O₂, S₆O₂, and S_(n)O_(x),where n and x are any possible stoichiometric numerical values).

In the event that the above definitions or a description statedelsewhere in this application is inconsistent with a meaning (explicitor implicit) that is commonly used, set forth in a dictionary, or statedin a source incorporated by reference into this application, theapplication and the claim terms in particular are understood to beconstrued according to the definition or description in thisapplication, and not according to the common definition, dictionarydefinition, or the definition that was incorporated by reference. In theevent that a claim term can only be understood if it is construed by adictionary, a definition set forth in the Kirk-Othmer Encyclopedia ofChemical Technology, 5th Edition, 2005, (John Wiley & Sons, Inc.) shallcontrol, if provided therein.

The disclosure provides apparatus and methods for treating acid gas withrespect to none, some, or all of the following problems of the prior artin using ammonia desulfurization to treat acid tail gas: inability ofachieving long-period stable operation of the device, poor productquality, and difficulty in headstream-controlling ammonia escape and theproduction of aerosol.

The apparatus and methods for treating acid gas may include the use ofan ammonia desulfurization process to treat acid tail gas, and mayachieve the discharge of net tail gas meeting the standard throughmulti-stage circulating absorption and efficient acid tail gas treatmentwith low cost. Here, the multi-stage circulating absorption of ammoniadesulfurization may include one or more of a cooling cycle, an SO₂absorption cycle, and a water-washing cycle.

It may be advantageous to adjust the enthalpy values of the acid tailgases obtained as described above by a regulatory system at first, andthen feed the acid tail gases into a subsequent ammonia desulfurizationprocess.

The enthalpy value of acid tail gas has an effect on the stablestandardized operation of the desulfurization device: when the enthalpyvalue is high and the absorption temperature is high, ammonia escape maybe significant, and thus absorption efficiency cannot be guaranteed;whereas, when the enthalpy value is low and the absorption temperatureis low, oxidation rate of circulating absorption liquid may be low andthus the post-treatment system cannot be operated stably, moreover,since the sulfur-recovered tail gas may be incompletely incinerated inan incineration system, hydrogen sulfide tends to be converted intosulfur when incinerated at a lower temperature, and hydrogen sulfide,elementary sulfur and organic matters in turn may affect the oxidationof ammonium sulfite and the crystallization of ammonium sulfate, causingthe poor product quality. If it is desirable to incinerate virtually allof the hydrogen sulfide, organic matters and elementary sulfur in theacid gas or sulfur-recovered tail gas through the incineration system,the incineration temperature may need to be raised to 1,300° C. orhigher, the coefficient of excess air may need to be raised to 1.8, andthe residence time may need to be raised to 7 s. However, this mayincrease the investment and operating cost of the incineration systemand may consume a large amount of fuel gas; moreover, the incineratedflue gas may contain a high concentration of nitrogen oxides, thedenitrification investment may be large with high operating cost, andthe nitrogen oxide content of the final effluent gas may not easily meetthe standard.

The enthalpy value of the acid tail gas should be appropriatelycontrolled within the range of 60-850 kJ/kg dry gas, for example, 80-680kJ/kg dry gas or 100-450 kJ/kg dry gas, before entering the process ofammonia desulfurization.

The regulatory system may include a temperature adjustment unit and/or ahumidity adjustment unit or both of a temperature adjustment unit and ahumidity adjustment unit. The enthalpy value of acid tail gas may becontrolled by measuring the temperature and humidity of the acid tailgas which will enter the process of ammonia desulfurization, and byadjusting the temperature and humidity of the tail gas with theregulatory system.

An illustrative formula of the enthalpy value of tail gas isH=(1.01+1.88b)*t+2490b, wherein t is temperature in ° C., and b is watervapor content in dry gas in kg/kg dry gas.

Those skilled in the art will appreciate that, depending on differenttemperatures and humidities of the acid tail gas itself to be treated inthe regulatory system, the temperature adjustment unit may accordinglycomprise a heating or cooling apparatus, for example, a heater or cooleror other temperature control apparatus, while the humidity adjustmentunit may accordingly comprise a humidifying or dehumidifying apparatus,such as an apparatus that can perform nitrogen or carbon dioxide gasdistribution or add water vapor. Suitable temperature regulatingapparatus and humidity regulating apparatus themselves are well known tothose skilled in the art.

The regulatory system further may include one or more of a sulfurremoval unit, a dust removal unit, and an impurity removal unit. Thus,the total dust content of the acid tail gas may be adjusted by theregulatory system, and the total acid dust content of the acid tail gasafter adjustment may be ≤200 mg/Nm³, for example, ≤50 mg/Nm³.

The impurity content of the acid tail gas can be adjusted by theregulatory system, and the organic matter content of the acid tail gasafter adjustment may be ≤30 ppm, for example ≤10 ppm, and/or theelementary sulfur and hydrogen sulfide content may be ≤30 ppm, forexample ≤10 ppm.

The circulating absorption liquid of ammonia desulfurization may besubjected to a purification treatment such that the suspended mattercontent in the circulating absorption liquid may be ≤200 mg/L and/or theoil content may be ≤100 mg/L.

There are no special restrictions on the source of acid tail gasapplicable to the apparatus and methods, as long as they are commonlyused in the petrochemical, natural gas chemical, coal chemicalindustries and the like. Here, the acid tail gas may include,illustratively, the tail gas obtained after treating the petrochemical,natural gas chemical, and coal chemical acid gas with a process such assulfur recovery plus incineration, sulfuric acid production, andincineration; or the acid tail gas may include, illustratively,catalytic cracking regeneration flue gas.

The sulfur recovery may include a sulfur recovery process, such as a 1to 3-stage Claus sulfur recovery process, a SuperClaus sulfur recoveryprocess, an EuroClaus sulfur recovery process, a liquid-phase catalyticoxidation sulfur recovery process or a biological sulfur recoveryprocess; and the sulfuric acid production process may be performed witha wet sulfuric acid production process or a dry sulfuric acid productionprocess.

The molar ratio of H₂S/SO₂ in the sulfur-recovered tail gas may becontrolled at 1.2-3, for example, 1.5-2.5.

In the sulfur recovery plus incineration process and the incinerationprocess, the incineration temperature may be 600° C.-1,300° C., forexample, 650° C.-950° C., the residence time may be 1-6 s, for example,1.5-4 s, the oxygen content of the acid tail gas may be 2%-5%, forexample, 3%-4%, and sulfur oxide content of the acid tail gas may be2,000-150,000 mg/Nm³, for example 5,000-55,000 mg/Nm³.

The methods may include the process steps:

1) acid gas is treated by sulfur recovery plus incineration or sulfuricacid production or incineration, or directly by catalytic crackingcatalyst regeneration process to obtain acid tail gas;

2) the acid tail gas is fed into the regulatory system to adjust theenthalpy value of the tail gas to be within the range of 60-850 kJ/kgdry gas, for example, 80-680 kJ/kg dry gas or 100-450 kJ/kg dry gas;

3) the acid tail gas which meets the enthalpy value requirement is fedinto the ammonia desulfurization process for treatment, to achieve thepurpose that net tail gas meets the discharge standard throughmulti-stage circulating absorption.

The acid tail gas obtained in step 2) may be further treated in theregulatory system such that the total dust content is ≤200 mg/Nm³ and/orthe organic matter content is ≤30 ppm and/or the elementary sulfurcontent is ≤30 ppm before it is fed into the ammonia desulfurizationprocess.

The apparatus may include a device for treating acid gas, including anacid gas pre-treatment system and an ammonia desulfurization system.

The acid gas pre-treatment system may include one or more of a sulfurrecovery system plus incineration system, a sulfuric acid productionsystem, an incineration system, and a catalytic cracking catalystregeneration system. The ammonia desulfurization system may be aconventional ammonia desulfurization device, and its structure may beknown in the art, for example, reference may be made to CN201710379460.3, CN 201810057884.2 for which the applicant has applied.CN 201710379460.3, CN 201810057884.2 are hereby incorporated herein byreference in their entireties.

The sulfur recovery system may include one or more of a 1 to 3-stageClaus sulfur recovery system, a SuperClaus sulfur recovery system, anEuroClaus sulfur recovery system, a liquid-phase catalytic oxidationsulfur recovery system and biological sulfur recovery system.

The apparatus may include a regulatory system comprising a temperatureregulating apparatus and/or a humidity regulating apparatus, or both atemperature regulating apparatus and a humidity regulating apparatus.The regulatory system may include one or more of a sulfur removaldevice, a dust removal apparatus, and an impurity removal apparatus.

The acid gas pre-treatment system, the regulatory system, and theammonia desulfurization system may be connected successively. The acidgas pre-treatment system may include a sulfur recovery system plusincineration system. The regulatory system may include one or more of atemperature regulating apparatus, a humidity regulating apparatus, andan impurity removal apparatus that can be connected to each othersuccessively in any order, or one or more of an impurity removalapparatus, a temperature regulating apparatus, a humidity regulatingapparatus and an impurity removal apparatus that can be connected toeach other successively in any order.

The apparatus may include an absorption liquid treatment system that mayinclude one or more of a concentration apparatus, a solid-liquidseparation apparatus, and a drying apparatus.

The absorption liquid treatment system may include one or more of asolution purification apparatus and an evaporation crystallizationapparatus. The solution purification apparatus may include one or moreof an oil removal apparatus and a suspended matter removal apparatus.The suspended matter removal apparatus may be configured to form acirculating absorption liquid with a suspended matter content of ≤200mg/L, 20-100 mg/L, or 30-50 mg/L.

The oil removal apparatus may be configured to form a circulatingabsorption liquid with an oil content of ≤100 mg/L, for example 10-80mg/L or 20-30 mg/L. The oil removal apparatus may include one or more ofan air flotation apparatus, an adsorption apparatus or a precisionfiltration apparatus, or a combination thereof.

The oil removal apparatus may be connected to the incineration system.

The acid gas derived from petrochemical industry may be subjected tosulfur recovery plus incineration (pre-treatment) to obtain an acid tailgas, and then the enthalpy value of the acid tail gas may be adjustedwith a regulatory system before it is fed into the ammoniadesulfurization process. Here, the multi-stage circulating absorption ofammonia desulfurization may include a 1-stage cooling cycle, a 2-stageSO₂ absorption cycle, and a 1-stage water-washing cycle.

The regulatory system may include one or more of a temperatureregulating unit, a humidity regulating unit and a sulfur removal unitthat are connected successively. The enthalpy value of the acid tail gasmay be first adjusted to 560-720 kJ/kg dry gas through a coolingapparatus, and then the low-temperature low-enthalpy nitrogen gas may besupplemented through a dehumidifying apparatus to further adjust theacid tail gas's enthalpy value to 440-530 kJ/kg dry gas. Then, theelementary sulfur and hydrogen sulfide content of the tail gas may beregulated and controlled to 4-7.5 ppm through an adsorptionsulfur-removal apparatus.

The hydrogen sulfide content of the acid gas may be, for example, about90%, the rest being nitrogen, carbon dioxide, and the sulfur recoverysystem for treating the acid gas may include an air-method 3-stage Claussulfur recovery process. The molar ratio of H₂S/SO₂ in thesulfur-recovered tail gas may be controlled at 1.7-2.8, the incinerationtemperature of the incineration system may be 850° C.-950° C., theresidence time may be 2-4 s, the oxygen content of the acid tail gas maybe about 3%, and the sulfur oxide content in the incinerated tail gasmay be about 12,000-15,000 mg/Nm³.

For an illustrative flow rate of an acid gas of 46,000 Nm³/h, the sulfurrecovery rate may be 96%, the annual operating time may be 8,400 h, and477,000 tons of sulfur per year and 80,500 tons of ammonium sulfate peryear may be obtained after the treatment.

If the regulatory system is not used to control the organic mattercontent of the acid tail gas, the circulating absorption liquid ofammonia desulfurization may be subjected to the treatment of oil removalto render the oil content of the circulating absorption liquid ≤50 mg/L.

An illustrative acid gas treatment apparatus may include one or more ofan acid gas pre-treatment system (sulfur recovery system plusincineration system), a regulatory system, and an ammoniadesulfurization system.

The sulfur recovery system may include a thermal reaction plus 3-stageClaus catalytic reaction apparatus, and the Claus catalytic recoverermay be a recoverer that is not charged with a hydrolysis catalyst.

The regulatory system may include one or more of a temperatureregulating apparatus, a humidity regulating apparatus and a sulfurremoval device that are connected successively.

The sulfur recovery system, incineration system, regulatory system andammonia desulfurization system for acid gas may be connectedsuccessively. The temperature regulating apparatus may be a two-stagewaste heat recovery apparatus, the by-product of first-stage waste heatrecovery may be saturated steam, and the second-stage waste heatrecovery may preheat boiler feed water; and the humidity regulatingapparatus may include a nitrogen gas distribution apparatus.

The apparatus make include an absorption liquid treatment system, whichmay include one or more of a concentration apparatus, a solid-liquidseparation apparatus, and a drying apparatus.

The absorption liquid treatment system may include a solutionpurification apparatus. The solution purification apparatus may includean oil removal apparatus, which may be configured to form a circulatingabsorption liquid with an oil content of ≤50 mg/L. The oil removalapparatus may include an air flotation apparatus plus precisionfiltration apparatus.

The oil removal apparatus may be connected to the incineration system,and the waste oil may be completely incinerated into water, carbondioxide and sulfur dioxide in the incineration system.

With regard to the apparatus and methods, reference can be made to theauthorized series patents of ammonia desulfurization, such as CN200510040801.1, CN 03158258.3, CN 201010275966.8, CN 200510040800.7, CN03158257.5 and the like, and CN 201710379460.3, CN 201710379458.6, CN201710154157.3, CN 201710800599.0, CN 201710865004.X, and CN201810329999.2 under examination.

Compared with prior acid gas treatment process, by specifying the acidtail gas control parameters, using the pre-treatment plus adjustmentplus ammonia desulfurization process to treat the acid gas, especiallyby controlling the enthalpy value of the acid tail gas, the apparatusand methods may reduce the investment and operating cost of the ammoniadesulfurization system, may achieve long-period stable operation, mayachieve synergistic control of acid gas pre-treatment and ammoniadesulfurization of acid tail gas, may improve ammonia recovery rate, maycontrol the production of aerosol, and may improve the product quality.

Apparatus and methods for treating acid gas are provided. The apparatusmay include, and the methods may involve an acid gas pre-treatmentsystem; and, in fluid communication with the acid gas pre-treatmentsystem, an ammonia desulfurization system.

The pretreatment system may include one or more of a sulfur recoverysystem plus incineration system, a sulfuric acid production system; anda catalytic cracking catalyst regeneration system. The sulfur recoverysystem may include a Claus sulfur recovery system. The Claus sulfurrecovery system may be a one-stage Claus sulfur recovery system. TheClaus sulfur recovery system may be a two-stage Claus sulfur recoverysystem. The Claus sulfur recovery system may be a three-stage Claussulfur recovery system.

The sulfur recovery system may include a liquid-phase catalyticoxidation sulfur recovery system. The sulfur recovery system may includea biological sulfur recovery system.

The sulfur recovery system may include, in fluid communication with theClaus sulfur recovery system, a SuperClaus sulfur recovery system.

The sulfur recovery system may include, in fluid communication with theClaus sulfur recovery system, a EuroClaus sulfur recovery system.

The sulfur recovery system may include, in fluid communication with theClaus sulfur recovery system, a biological sulfur recovery system.

The sulfur recovery system may include, in fluid communication with theClaus sulfur recovery system, a liquid-phase catalytic oxidation sulfurrecovery system

The apparatus may include a regulatory system that is in fluidcommunication with, and upstream from, the ammonia desulfurizationsystem. The regulatory system may include a temperature regulatorconfigured to regulate a gas temperature in the regulatory system. Theregulatory system may include a humidity regulator configured toregulate a gas humidity in the regulatory system.

The apparatus may include a sulfur removal device in fluid communicationwith the ammonia desulfurization system. The apparatus may include adust removal apparatus in fluid communication with the ammoniadesulfurization system.

The apparatus may include an impurity removal apparatus in fluidcommunication with the ammonia desulfurization system.

The apparatus may include a sulfur removal device in fluid communicationwith the ammonia desulfurization system; and a dust removal apparatus influid communication with the ammonia desulfurization system.

The apparatus may include a sulfur removal device in fluid communicationwith the ammonia desulfurization system; and an impurity removalapparatus in fluid communication with the ammonia desulfurizationsystem.

The apparatus may include a dust removal apparatus in fluidcommunication with the ammonia desulfurization system; and an impurityremoval apparatus in fluid communication with the ammoniadesulfurization system.

The acid gas pre-treatment system; the regulatory system; and theammonia desulfurization system may be connected successively along adownstream direction.

The acid gas pre-treatment system may include a sulfur recovery systemplus incineration system.

The apparatus may include a regulatory system that is in fluidcommunication with, and upstream from, the ammonia desulfurizationsystem. The regulatory system may include a temperature regulatorconfigured to regulate a gas temperature in the regulatory system. Theregulatory system may include a humidity regulator configured toregulate a gas humidity in the regulatory system.

The apparatus may include a sulfur removal device in fluid communicationwith the ammonia desulfurization system.

The acid gas pre-treatment system; the regulatory system; and theammonia desulfurization system may be connected successively along adownstream direction.

The acid gas pre-treatment system may include a sulfur recovery systemplus incineration system. In the regulatory system, the temperatureregulator, humidity regulator and a the sulfur removal device may beconnected successively in the downstream direction. In the regulatorysystem, the temperature regulator, humidity regulator and a the sulfurremoval device are connected successively in the downstream direction.

The ammonia desulfurization system: may be configured to circulateammonia-containing absorption liquid; and may include an absorptionliquid treatment system that may include one or more of: a concentrationdevice configured to receive the absorption liquid; a solid-liquidseparation device configured to collect solids suspended in the liquid;and a drying device configured to dry the collected solids.

The absorption liquid treatment system may include a solutionpurification device in fluid communication with, and disposed in adirection operationally downstream from, the solid-liquid separationdevice. The absorption liquid treatment may system includes anevaporation crystallization device that: may be in fluid communicationwith one or both of: the concentration device; and the solid-liquidseparation device; and may be disposed, operationally: downstream fromthe concentration device; and upstream from the solid-liquid separationdevice.

The absorption liquid treatment system may include an evaporationcrystallization device that may be: in fluid communication with one orboth of: the concentration device; and the solid-liquid separationdevice; and may be disposed, operationally: downstream from theconcentration device; and upstream from the solid-liquid separationdevice.

The solution purification device may include an oil removal device thatis in fluid communication with the solid-liquid separation device.

The solution purification device may include a suspended matter removaldevice that is in fluid communication with the solid-liquid separationdevice.

The solution purification device may include a suspended matter removaldevice that is in fluid communication with the solid-liquid separationdevice.

The suspended matter removal device may be configured to provide acirculating absorption liquid that has a suspended matter content nogreater than 200 mg/L. The suspended matter content may be in the range20-100 mg/L. The suspended matter content may be in the range 30-50mg/L.

The oil removal device may include, in fluid communication with thesolid-liquid separation device, an air flotation device.

The oil removal device may include, in fluid communication with thesolid-liquid separation device, an adsorption device.

The oil removal device may include, in fluid communication with thesolid-liquid separation device, a precision filtration device.

The oil removal device may include, in fluid communication with thesolid-liquid separation device, an adsorption device.

The oil removal device may include, in fluid communication with thesolid-liquid separation device, a precision filtration device.

The oil removal device further includes, in fluid communication with thesolid-liquid separation device, a precision filtration device.

The oil removal device may be configured to produce a circulatingabsorption liquid having an oil content no greater than 100 mg/L. Theoil content may be in the range 10-80 mg/L. The oil content may be inthe range 20-30 mg/L. The oil removal device may be in fluidcommunication with, and disposed operationally upstream from, theincineration system. The methods may include receiving acid gas; andderiving from the acid gas: one or both of ammonium sulfate; and nettail gas that meets a discharge standard. The discharge standard may bea standard defined in the document entitled, “Emission Standard ofPollutants for Petroleum Refining Industry,” published as China,GB31570-2015, which is hereby incorporated by reference herein in itsentirety.

The discharge standard may be a standard defined in the documententitled, “Emission Standard of Pollutants for Petroleum ChemistryIndustry,” published as China, GB31571-2015, which is herebyincorporated by reference herein in its entirety. Illustrative examplesof pollutant emission standards

“Emission Standard of Pollutant for Oil Refining Industry” Tables 3 4,excerpted below, show the pollutant emission standards of regeneratedflue gas for process heating furnaces, FCC catalyst regeneration fluegas, particulate matter in tail gas of acid gas recovery plants, nickeland its compounds, sulfur dioxide and sulfuric acid mist. From “EmissionStandard of Pollutant for Oil Refining Industry”

TABLE 3 Special Emission Limits of Air Pollutants (Units of Measurement:mg/m³) Location of Acid gas recovery Pollutant Emission NumberPollutants devices Monitoring Device 1 particulate matter — Exhaust pipefor 2 nickel and its — workshop or compounds production facility 3sulfur dioxide 400 4 nitrogen oxides 5 sulphuric acid mist    30(4) 6hydrogen chloride — 7 pitch fume — 8 benzo(a)pyrene — 9 benzene — 10toluene — 11 xylene — 12 NMHC —

From “Emission Standard of Pollutant for Oil Refining Industry”

TABLE 4 Special Emission Limits of Air Pollutants (Units of Measurement:mg/m3) Process FCC catalyst Acid gas Location of heating regenerationrecovery Pollutant Emission Number Pollutants furnace flue gas (1)devices Monitoring Device 1 particulate matter n/a 30 — Exhaust pipe for2 nickel and its — 0.3 — workshop or compounds production facility 3sulfur dioxide 50 50 100 4 nitrogen oxides 100 100 — 5 sulphuric acid ——    5(3) mist 6 hydrogen — — — chloride 7 pitch fume — — — 8benzo(a)pyrene — — — 9 benzene — — — 10 toluene — — — 11 xylene — — — 12NMHC — — — Notes (1) The maximum value of the concentration of theregenerated flue gas pollutants in the catalytic cracking waste heatboiler does not exceed 2 times of the limit value in the table, and thetime duration of each time is not greater than 1 hour.

“Emission Standard of Pollutant for Petroleum Chemistry Industry” Tables4 and 5, excerpted below, show emission requirements of particulatematters and sulfur dioxide in tail gas of process heating furnacedevice.

From “Emission Standard of Pollutant for Petroleum Chemistry Industry”

TABLE 4 Emission Limits of Air Pollutants (Part) (Units of Measurement:mg/m3) Process Location of heating Pollutant Emission Number Pollutantsfurnace Monitoring Device 1 particulate matter  20 Exhaust pipe for 2sulfur dioxide 100 workshop or 3 nitrogen oxides 150 production facility  180(3)

From “Emission Standard of Pollutant for Petroleum Chemistry Industry”

TABLE 5 Special Emission Limits of Air Pollutants (Part) (Units ofMeasurement: mg/m3) Process Location of heating Pollutant EmissionNumber Pollutants furnace Monitoring Device 1 particulate matter 20Exhaust pipe for 2 sulfur dioxide 50 workshop or 3 nitrogen oxides 100production facility

The deriving may include: one or both of recovering sulfur from the acidgas to produce sulfur-recovered tail gas; and, then, incinerating thesulfur-recovered gas.

The deriving may include producing sulfuric acid from the acid gas.

The deriving may include incinerating.

The method may include channeling the acid gas from a petrochemicalchemical reaction. The method may include channeling the acid gas from anatural gas chemical reaction. The method may include channeling theacid gas from a coal chemical reaction.

The deriving may include generating catalytic cracking regeneration fluegas. The acid tail gas may include the regeneration flue gas.

The deriving may include adjusting an enthalpy value of acid tail gas.

The deriving may include passing adjusted tail gas through one or moreof: a cooling stage, an absorption stage, and a water-washing stage, allin an ammonia circulation desulfurization reactor.

The adjusting may include changing a temperature of the acid tail gas.

The adjusting may include changing a humidity of the acid tail gas.

The adjusting may include changing a temperature of the acid tail gas.

The adjusting may include removing sulfur from the acid tail gas.

The adjusting may include removing dust from the acid tail gas.

The adjusting may include removing an impurity from the acid tail gas.

The adjusting may adjust the value to 60-850 kJ/kg dry gas. Theadjusting may adjust the value to 80-680 kJ/kg dry gas. The adjustingmay adjust the value to 100-450 kJ/kg dry gas.

The recovering may include flowing the acid gas through a Claus sulfurrecovery system having 1 stage. The recovering may include flowing theacid gas through a Claus sulfur recovery system having 2 stages. Therecovering may include flowing the acid gas through a Claus sulfurrecovery system having 3 stages.

The recovering may include flowing the acid gas through a liquid-phasecatalytic oxidation sulfur recovery system. The recovering may includeflowing the acid gas through a biological sulfur recovery system. Therecovering may include flowing the acid gas through a SuperClaus sulfurrecovery system. The recovering may include flowing the acid gas througha EuroClaus sulfur recovery system. The recovering further includesflowing the acid gas through a biological sulfur recovery system. Therecovering may include flowing the acid gas through a liquid-phasecatalytic oxidation sulfur recovery system.

The sulfuric acid production may include wet sulfuric acid production.The sulfuric acid production may include dry sulfuric acid production.

The recovering may include producing sulfur-recovered gas having a molarratio H₂S/SO₂ in the range 1.2-3. The molar ratio may be in the range1.5-2.5.

The incinerating may be performed at a temperature in the range 600°C.-1,300° C. The incinerating may produce an acid tail gas.

In the incinerating, the sulfur-recovered tail gas may have a residencetime in the range 1 to 6 s.

The acid tail gas may have an oxygen content in the range 2%-5%.

The acid tail gas may have a sulfur oxide content in the range 2,000mg/Nm³ to 150,000 mg/Nm³. The incinerating may be performed at atemperature in the range 650° C. to 950° C.

In the incinerating, the sulfur-recovered tail may have a residence timein the range 1.5 to 4 s.

The acid tail gas may have an oxygen content in the range 3%-4%.

The acid tail gas may have a sulfur oxide content in the range 5,000mg/Nm³ to 55,000 mg/Nm³.

The method may include producing an acid tail gas having a sulfur oxidecontent in the range 2,000 mg/Nm³ to 150,000 mg/Nm³.

The incinerating may be performed at a temperature in the range 600°C.-1,300° C. The incinerating may produce the acid tail gas.

The method may include incinerating sulfur-recovered tail gas having anincineration residence time in the range 1 to 6 s.

The acid tail gas may have an oxygen content in the range 2%-5%.

The incinerating may be performed at a temperature in the range 650° C.to 950° C.

In the incinerating, the sulfur-recovered tail gas may have a residencetime in the range 1.5 to 4 s.

The acid tail gas may have an oxygen content in the range 3%-4%.

The acid tail gas may have a sulfur oxide content in the range 5,000mg/Nm³ to 55,000 mg/Nm³.

The method may include producing an acid tail gas having an oxygencontent in the range 2%-5%.

The acid tail gas may have a sulfur oxide content in the range 2,000mg/Nm³ to 150,000 mg/Nm³.

The incinerating may be performed at a temperature in the range 600°C.-1,300° C. The incinerating may produce the acid tail gas.

In the incinerating, the sulfur-recovered tail gas may have a residencetime in the range 1 to 6 s.

The incinerating may be performed at a temperature in the range 650° C.to 950° C.

In the incinerating, the sulfur-recovered tail gas may have a residencetime in the range 1.5 to 4 s.

The acid tail gas may have an oxygen content in the range 3%-4%.

The acid tail gas may have a sulfur oxide content in the range 5,000mg/Nm³ to 55,000 mg/Nm³.

In the incinerating, the sulfur-recovered tail gas may have a residencetime in the range 1 to 6 s.

The method may include producing acid tail gas having an oxygen contentin the range 2%-5%.

The method may include producing acid tail having a sulfur oxide contentin the range 2,000 mg/Nm³ to 150,000 mg/Nm³.

The incinerating may be performed at a temperature in the range 600°C.-1,300° C. The incinerating may produce the acid tail gas.

The incinerating may be performed at a temperature in the range 650° C.to 950° C.

In the incinerating, the sulfur-recovered tail gas may have a residencetime in the range 1.5 to 4 s.

The acid tail gas may have an oxygen content in the range 3%-4%.

The acid tail gas may have a sulfur oxide content in the range 5,000mg/Nm³ to 55,000 mg/Nm³.

The deriving may include reducing a suspended matter content of anammonia desulfurization circulating absorption liquid to no greater than200 mg/L.

The deriving may include reducing an oil content of an ammoniadesulfurization circulating absorption liquid to no greater than 100mg/L.

The deriving may include reducing an oil content of an ammoniadesulfurization circulating absorption liquid to no greater than 100mg/L.

The adjusting may produce adjusted tail gas having an organic mattercontent not greater than 30 ppm.

The adjusting may produce adjusted tail gas having an elementary sulfurand hydrogen sulfide content not greater than 30.

The adjusting may produce adjusted tail gas having an organic mattercontent not greater than 10 ppm.

The adjusting may produce adjusted tail gas having an elementary sulfurand hydrogen sulfide content not greater than 10 ppm.

The acid gas may be treated by sulfur recovery plus incineration orsulfuric acid production or incineration, or directly by catalyticcracking catalyst regeneration process to obtain acid tail gas.

The acid tail gas may be fed into the regulatory system to adjust theenthalpy value of the tail gas to be within the range of 60-850 kJ/kgdry gas, for example, 80-680 kJ/kg dry gas, or 100-450 kJ/kg dry gas.

Acid tail gas meeting a selected enthalpy criterion may be fed into theammonia desulfurization process for treatment, to achieve the purposethat net tail gas meets a discharge standard through multi-stagecirculating absorption.

Some embodiments may omit features shown and/or described in connectionwith the illustrative apparatus. Some embodiments may include featuresthat are neither shown nor described in connection with the illustrativeapparatus. Features of illustrative apparatus and methods may becombined. For example, one illustrative embodiment may include featuresshown in connection with another illustrative embodiment.

The steps of illustrative methods may be performed in an order otherthan the order shown and/or described herein. Some embodiments may omitsteps shown and/or described in connection with the illustrativemethods. Some embodiments may include steps that are neither shown nordescribed in connection with the illustrative methods. Illustrativemethod steps may be combined. For example, one illustrative method mayinclude steps shown in connection with another illustrative method.

Embodiments may involve some or all of the features of the illustrativeapparatus and/or some or all of the steps of the illustrative methods.

Apparatus and methods described herein are illustrative. Apparatus andmethods in accordance with the invention will now be described inconnection with the Examples and the FIGs, which form a part hereof. TheFIGS. show illustrative features of apparatus and method steps inaccordance with the principles of the invention. It is to be understoodthat other embodiments may be utilized and that structural, functionaland procedural modifications may be made without departing from thescope and spirit of the present invention.

ILLUSTRATIVE EXAMPLES Example 1

Acid gas 1 derived from petrochemical industry was used. The acid gas 1was passed through a sulfur recovery system 2 to obtain sulfur-recoveredtail gas 6, and then passed through an incineration system 5 to obtainacid tail gas 6 (pre-treatment system). The enthalpy value of the acidtail gas was adjusted by a regulatory system 7, and then the adjustedtail gas 8 was fed into an ammonia desulfurization system 10 to whichammonia 9 was introduced. The multi-stage circulating absorption of theammonia desulfurization system 10 included a 1-stage cooling cycle, a2-stage SO₂ absorption cycle, and a 2-stage water-washing cycle.

The adjusting system 7 herein as shown in FIG. 3 included an impurityremoval apparatus 17, a cooling apparatus 14, a dehumidifying apparatus15, and a sulfur removal device 16 which were connected successively.The organic matter content of the acid tail gas was reduced to 4.5 ppmor lower by the impurity removal apparatus 17, the enthalpy value of theacid tail gas 6 was further adjusted to 600-810 kJ/kg dry gas throughthe cooling apparatus 14, and then the low-temperature carbon dioxidegas with a low water vapor content was supplemented through thedehumidifying apparatus 15 to further adjust the enthalpy value of theacid tail gas 6 to 410-505 kJ/kg dry gas. Then, the elementary sulfurand hydrogen sulfide content of the adjusted tail gas 8 was controlledto 3 ppm or lower by adsorbing sulfur and hydrogen sulfide in the tailgas through the adsorption sulfur-removal apparatus 16.

In this example, the hydrogen sulfide content of the acid gas 1 was 75%,and the rest were nitrogen, carbon dioxide, hydrogen, and carbonmonoxide; and the sulfur recovery system 2 adopted the air-method2-stage Claus sulfur recovery process. The molar ratio of H₂S/SO₂ in thesulfur-recovered tail gas 4 was controlled at 1.4-2.2, the incinerationtemperature of the incineration system 5 was 750° C.-810° C., theresidence time was 2-2.8 s, the oxygen content of the acid tail gas was2.8%, and the sulfur oxide content was 22,400 mg/Nm³.

The flow rate of the acid gas 1 was 8,100 Nm³/h, the sulfur recoveryrate was 93.6%, the annual operating time was 8,400 h, 68,200 tons ofsulfur 3 per year and 19,000 tons of ammonium sulfate 11 per year wereobtained, and the ammonia recovery rate was 99.1%.

Accordingly, the apparatus for carrying out the above-mentionedtreatment method in this example comprises an acid gas pre-treatmentsystem (sulfur recovery system plus incineration system), a regulatorysystem, and an ammonia desulfurization system which are connectedsuccessively.

The sulfur recovery system included a blower apparatus, a thermalreaction apparatus and a 2-stage Claus catalytic reaction apparatus.

In addition, the regulatory system included the impurity removalapparatus, cooling apparatus, dehumidifying apparatus anddesulfurization apparatus which were connected successively. Theimpurity removal apparatus was a catalytic oxidation apparatus, thedesulfurization apparatus was an activated carbon adsorption apparatus,the cooling apparatus was a one-stage waste heat recovery, with theby-product of 0.3-0.5 MPa saturated steam, and the dehumidifyingapparatus was connected to a carbon dioxide gas source.

The apparatus included an absorption liquid treatment system, whichincluded a concentration circulating tank, a solid-liquid separationapparatus, and a drying apparatus. The ammonia desulfurization systemadopted a saturated crystallization process in the tower.

The amount of the adjusted tail gas was 68,450 Nm³/h (standard state,wet base, actual oxygen), the SO₂ concentration was 16,100 mg/Nm³, thetower had a diameter of 3.2 m and a height of 42 m, the sulfur dioxidecontent of the net tail gas was 32.4 mg/Nm³, the free ammonia was 1.3mg/Nm³, and the total dust was 9.5 mg/Nm³.

For the ammonia desulfurization apparatus and methods in this example,reference can be made to CN 201710379460.3, CN 201710865004.X, and CN201810329999.2.

Example 2

Acid gas 1 derived from natural gas chemical industry was used. The acidgas 1 was passed through a sulfuric acid production system 13 to obtainsulfuric acid 3 and acid tail gas 6, and then the enthalpy value of theacid tail gas was adjusted by a regulatory system 7. Then the adjustedtail gas was fed into the ammonia desulfurization system 10 to whichammonia 9 was added. The multi-stage circulating absorption of theammonia desulfurization system 10 included a 1-stage cooling cycle, a1-stage SO₂ absorption cycle, and a 1-stage water-washing cycle.

Here, the regulatory system 7 was a water vapor addition apparatus, andthe enthalpy value of the acid tail gas 6 was adjusted to 320-410 kJ/kgdry gas by adding water vapor.

In the acid gas 1 used, the hydrogen sulfide content was 45%, the CO₂content was 30%, and the rest were nitrogen, hydrogen, carbon monoxideand methane. The sulfuric acid production system 13 adopted a wetsulfuric acid production process. The sulfur oxide content in the acidtail gas was 5,350 mg/Nm³.

The flow rate of the acid gas 1 was 7,200 Nm³/h, the sulfuric acidrecovery rate was 98%, the annual operating time was 8,400 h, and119,000 tons of sulfuric acid 3 per year and 3,200 tons of ammoniumsulfate 11 per year were obtained, and the ammonia recovery rate was99.4%.

Accordingly, the apparatus for carrying out the above-mentioned methodincluded a wet sulfuric acid production system, a regulatory system andan ammonia desulfurization system which were connected successively.

The wet sulfuric acid production system included an incinerationapparatus, a conversion apparatus and a condensing apparatus.

The regulatory system included a water vapor addition apparatus.

The apparatus included an absorption liquid treatment system, whichincluded a solid-liquid separation apparatus, a drying apparatus. Theammonia desulfurization system adopted a saturated crystallizationprocess in the tower.

The amount of the adjusted tail gas was 38,450 Nm³/h (standard state,wet base, actual oxygen), the SO₂ concentration was 4,830 mg/Nm³, thetower had a diameter of 2.6 m and a height of 33 m, the sulfur dioxidecontent of the net tail gas was 16.8 mg/Nm³, the free ammonia contentwas 0.6 mg/Nm³, and the total dust was 4.5 mg/Nm³.

For the ammonia desulfurization apparatus and methods in this example,reference can be made to CN 201710379460.3, CN 201710865004.X, and CN201810329999.2.

Example 3

Acid tail gas derived from a petrochemical catalytic cracking catalystregeneration was used. The enthalpy value of the acid tail gas wasadjusted by a regulatory system, and then the acid tail gas was fed intoan ammonia desulfurization system. The multi-stage circulatingabsorption of the ammonia desulfurization system included a 2-stagewashing cycle, a 1-stage SO₂ absorption cycle, and a 1-stagewater-washing cycle.

The regulatory system was a cooling apparatus, a dust removal apparatusand an impurity removal apparatus. The organic matter content wasreduced to 6.2 ppm or less by the impurity removal apparatus. Theenthalpy value of the acid tail gas was further adjusted to 370-408kJ/kg dry gas through the cooling apparatus. Then the total dust contentwas reduced to 20-30 mg/Nm³ by the dust removal apparatus.

The flow rate of the acid tail gas was 210,000 Nm³/h, the sulfur oxidecontent was 2,350 mg/Nm³, and the total dust content was 100-230 mg/Nm³.The annual operating time was 8,400 h, 4,100 tons of ammonium sulfateper year were obtained after the treatment of the ammoniadesulfurization system, and the ammonia recovery rate was 99.3%.

Accordingly, the apparatus for carrying out the above-mentioned methodincluded a catalytic cracking catalyst regeneration system, and theregulatory system and ammonia desulfurization system connectedsuccessively.

The regulatory system included a cooling apparatus, a dust removalapparatus, and an impurity removal apparatus.

The apparatus included an absorption liquid treatment system, whichincluded an evaporation crystallization apparatus, a solid-liquidseparation apparatus, and a drying apparatus.

The absorption liquid treatment system included a solution purificationapparatus. The solution purification apparatus included an oil removalapparatus and a suspended matter removal apparatus, which wereconfigured to form a circulating absorption liquid with an oil contentof ≤80 mg/L and a suspended matter content of ≤120 mg/L. The oil removalapparatus was an air flotation apparatus plus precision filtrationapparatus, and the suspended matter removal apparatus was a pressfiltration apparatus such as a plate and frame filter press.

The oil removal apparatus is connected to the incineration system, andthe waste oil was completely incinerated into water, carbon dioxide andsulfur dioxide in the incineration system.

The absorption tower had a diameter of 6 m and a height of 32 m, thesulfur dioxide content of the net tail gas was 23.3 mg/Nm³, the freeammonia content was 0.75 mg/Nm³, and the total dust was 14.5 mg/Nm³.

For the ammonia desulfurization apparatus and methods of this example,reference can be made to CN 201710379460.3 and CN 201810057884.2 forwhich have been applied by the applicant.

Comparative Example 1

Example 1 was repeated except that the acid tail gas was not adjusted bythe regulatory system 7, but the acid tail gas that had been subjectedto one-stage waste heat recovery was directly fed into the ammoniadesulfurization system. The parameters of the tail gas entering theammonia desulfurization system and the operation effects are compared asfollows:

Comparative Number Comparison item Unit Example 1 Example 1 1 Enthalpyvalue of the kJ/kg 410-505  910-1000 tail gas 2 Organic matter contentppm 4.5 37 of the tail gas 3 Sulfur and sulfide ppm 3 42 content of thetail gas 4 Absorption temperature ° C. 50-57 70-85 5 Sulfur dioxidecontent of mg/Nm³ 32.4 123 the net tail gas 6 Free ammonia content ofmg/Nm³ 1.3 26.8 the net tail gas 7 Total dust content of mg/Nm³ 9.5 47.9the net tail gas 8 Ammonia recovery rate % 99.1 94.3 of the ammoniadesulfurization system

It can be seen that the sulfur dioxide concentration, free ammoniacontent and total dust content of the net tail gas in ComparativeExample 1 were all higher than those in Example 1, and the ammoniarecovery rate was only 94.3%, which was 4.7% lower than that in Example1, resulting in a large amount of secondary pollution.

Comparative Example 2

Example 2 was repeated except that the acid tail gas was not adjusted bythe regulatory system 7, but the acid tail gas was directly fed into theammonia desulfurization system. The parameters of the tail gas enteringthe ammonia desulfurization system and the operation effects arecompared as follows:

Comparative Number Comparison item Unit Example 2 Example 2 1 Enthalpyvalue of the kJ/kg 320-410 30-52 tail gas 2 Absorption temperature ° C.47-50 30-35 3 Sulfur dioxide content of mg/Nm³ 16.8 37 the net tail gas4 Free ammonia content of mg/Nm³ 0.6 4.8 the net tail gas 5 Total dustcontent of mg/Nm³ 4.5 18.3 the net tail gas 6 Ammonia recovery rate %99.4 97.2 of the ammonia desulfurization system

It can be seen that the sulfur dioxide concentration, free ammoniacontent and total dust content of the net tail gas in ComparativeExample 2 were all higher than those in Example 2, and the ammoniarecovery rate was only 97.2%, which was 2.2% lower than that in Example2, resulting in a large amount of secondary pollution.

Comparative Example 3

Example 3 was repeated except that the acid tail gas was not adjusted bythe regulatory system, but the acid tail gas of the catalytic crackingcatalyst regeneration system that had been subjected to waste heatrecovery and denitrification was directly fed into the ammoniadesulfurization system. The parameters of the tail gas entering theammonia desulfurization system and the operation effects are compared asfollows:

Comparative Number Comparison item Unit Example 3 Example 3 1 Enthalpyvalue of the kJ/kg 370-408  930-1150 tail gas 2 Organic matter contentppm ≤6.2 18.9 of the tail gas 3 Total dust content of mg/Nm³ 20-30150-300 the tail gas 4 Absorption temperature ° C. 47.5-49.8 80-90 5Sulfur dioxide content of mg/Nm³ 23.3 169 the net tail gas 6 Freeammonia content of mg/Nm³ 0.75 33.7 the net tail gas 7 Total dustcontent of mg/Nm³ 14.5 102 the net tail gas 8 Ammonia recovery rate %99.3 91.3 of the ammonia desulfurization system

It can be seen that the sulfur dioxide concentration, free ammoniacontent and total dust content of the net tail gas in ComparativeExample 3 were all higher than those in Example 3, and the ammoniarecovery rate was only 91.3%, which was 8% lower than that in Example 3,resulting in a large amount of secondary pollution.

Some illustrative embodiments are identified below:

(A) A method for treating acid gas, wherein the ammonia desulfurizationprocess is used to treat acid tail gas, thereby achieving the purposethat net tail gas meets the discharge standard through multi-stagecirculating absorption.(B) The method of (A), wherein the acid tail gas comprises the tail gasobtained after treating the petrochemical, natural gas chemical, andcoal chemical acid gas with a process such as sulfur recovery plusincineration, sulfuric acid production, and incineration.(C) The method of (A), wherein the acid tail gas comprises catalyticcracking regeneration flue gas.(D) The method of any one of (B)-(C), wherein the enthalpy value of theacid tail gas is first adjusted by a regulatory system, and then theacid tail gas is fed into a subsequent ammonia desulfurization process.(E) The method of (A), wherein the multi-stage circulating absorptioncomprises a cooling cycle, an absorption cycle, and a water-washingcycle.(F) The method of (D), wherein the regulatory system comprises atemperature adjustment unit and/or a humidity adjustment unit, or both atemperature adjustment unit and a humidity adjustment unit.(G) The method of (F), wherein the regulatory system further comprisesone or more of a sulfur removal unit, a dust removal unit, and animpurity removal unit.(H) The method of (D), wherein the enthalpy value of the tail gas afterthe adjustment is within the range of 60-850 kJ/kg dry gas, for example,80-680 kJ/kg dry gas or 100-450 kJ/kg dry gas.(I) The method of (B), wherein the sulfur recovery is performed with asulfur recovery process, such as a 1 to 3-stage Claus sulfur recoveryprocess, a SuperClaus sulfur recovery process, an EuroClaus sulfurrecovery process, a liquid-phase catalytic oxidation sulfur recoveryprocess or a biological sulfur recovery process; and the sulfuric acidproduction process is performed with a wet sulfuric acid productionprocess or a dry sulfuric acid production process.(J) The method of (I), wherein the molar ratio of H₂S/SO₂ in thesulfur-recovered tail gas is controlled at 1.2-3, for example, 1.5-2.5.(K) The method of (B), wherein in the sulfur recovery plus incinerationprocess and the incineration process, the incineration temperature is600° C.-1,300° C., for example 650° C.-950° C., the residence time is1-6 s, for example 1.5-4 s, the oxygen content of the acid tail gas is2%-5%, for example, 3%-4%, and sulfur oxide content of the acid tail gasis 2,000-150,000 mg/Nm³, for example, 5,000-55,000 mg/Nm³.(L) The method of (A), wherein the circulating absorption liquid ofammonia desulfurization is subjected to a purification treatment suchthat the suspended matter content in the circulating absorption liquidis ≤200 mg/L and/or the oil content is ≤100 mg/L.(M) The method of (G), wherein the organic matter content of the tailgas after adjustment is ≤30 ppm, for example, ≤10 ppm, and/or theelementary sulfur and hydrogen sulfide content is ≤30 ppm, for example,≤10 ppm.(N) The method of any one of (A)-(M), wherein the specific process stepsinclude:1) acid gas is treated by sulfur recovery plus incineration or sulfuricacid production or incineration, or directly by catalytic crackingcatalyst regeneration process to obtain acid tail gas;2) the acid tail gas is fed into the regulatory system to adjust theenthalpy value of the tail gas to be within the range of 60-850 kJ/kgdry gas, for example, 80-680 kJ/kg dry gas or 100-450 kJ/kg dry gas;3) the acid tail gas which meets the enthalpy value requirement is fedinto the ammonia desulfurization process for treatment, to achieve thepurpose that net tail gas meets the discharge standard throughmulti-stage circulating absorption.(O) A apparatus for treating acid gas, wherein the apparatus comprisesan acid gas pre-treatment system and an ammonia desulfurization system.(P) The apparatus of (O), wherein the pre-treatment system comprises asulfur recovery system plus incineration system, a sulfuric acidproduction system, an incineration system, and a catalytic crackingcatalyst regeneration system.(Q) The apparatus of (P), wherein the sulfur recovery system comprises a1 to 3-stage Claus sulfur recovery system, a SuperClaus sulfur recoverysystem, an EuroClaus sulfur recovery system, a liquid-phase catalyticoxidation sulfur recovery system and biological sulfur recovery system.(R) The apparatus of (O), wherein the apparatus also comprises aregulatory system comprising a temperature regulating apparatus and/or ahumidity regulating apparatus, or both a temperature regulatingapparatus and a humidity regulating apparatus.(S) The apparatus of (Q), wherein the regulatory system furthercomprises one or more of a sulfur removal apparatus, a dust removalapparatus, and an impurity removal apparatus.(T) The apparatus of (S), wherein the acid gas pre-treatment system, theregulatory system, and the ammonia desulfurization system are connectedsuccessively, the acid gas pre-treatment system includes a sulfurrecovery system plus incineration system; and the regulatory systemincludes a temperature regulating apparatus, a humidity regulatingapparatus and a sulfur removal apparatus that are connectedsuccessively.(U) The apparatus of (O), wherein the apparatus further comprises anabsorption liquid treatment system, which comprises a concentrationapparatus, a solid-liquid separation apparatus, and a drying apparatus.(V) The apparatus of (U), wherein the absorption liquid treatment systemfurther comprises one or more of a solution purification apparatus andan evaporation crystallization apparatus.(W) The apparatus of (V), wherein the solution purification apparatusmay include one or more of an oil removal apparatus and a suspendedmatter removal apparatus.(X) The apparatus of (W), wherein the suspended matter removal apparatusis configured to form a circulating absorption liquid with a suspendedmatter content of ≤200 mg/L, for example, 20-100 mg/L or 30-50 mg/L.(Y) The apparatus of (W), wherein the oil removal apparatus is an airflotation apparatus, an adsorption apparatus or a precision filtrationapparatus, or a combination thereof.(Z) The apparatus of (Y), wherein the oil removal apparatus isconfigured to form a circulating absorption liquid with an oil contentof ≤100 mg/L, for example, 10-80 mg/L or 20-30 mg/L.(AA) The apparatus of any one of (V)-(Z), wherein the oil removalapparatus is connected to the incineration system.

-   -   1. Apparatus for treating acid gas, the apparatus comprising:    -   an acid gas pre-treatment system; and,    -   in fluid communication with the acid gas pre-treatment system,        an ammonia desulfurization system.    -   2. The apparatus of embodiment 1 wherein the pre-treatment        system includes a sulfur recovery system plus incineration        system.    -   3. The apparatus of embodiment 1 wherein the pre-treatment        system includes a sulfuric acid production system.    -   4. The apparatus of embodiment 1 wherein the pre-treatment        system includes a catalytic cracking catalyst regeneration        system.    -   5. The apparatus of embodiment 2 wherein the sulfur recovery        system includes a Claus sulfur recovery system having 1 stage.    -   6. The apparatus of embodiment 2 wherein the sulfur recovery        system includes a Claus sulfur recovery system having 2 stages.    -   7. The apparatus of embodiment 2 wherein the sulfur recovery        system includes a Claus sulfur recovery system having 3 stages.    -   8. The apparatus of embodiment 2 wherein the sulfur recovery        system includes a liquid-phase catalytic oxidation sulfur        recovery system    -   9. The apparatus of embodiment 2 wherein the sulfur recovery        system includes a biological sulfur recovery system.    -   10. The apparatus of any of embodiments 5 to 7 wherein the        sulfur recovery system further includes, in fluid communication        with the Claus sulfur recovery system, a SuperClaus sulfur        recovery system.    -   11. The apparatus of any of embodiments 5 to 7 wherein the        sulfur recovery system further includes, in fluid communication        with the Claus sulfur recovery system, a EuroClaus sulfur        recovery system.    -   12. The apparatus of any of embodiments 5 to 7 wherein the        sulfur recovery system further includes, in fluid communication        with the Claus sulfur recovery system, a biological sulfur        recovery system.    -   13. The apparatus of any of embodiments 5 to 7 wherein the        sulfur recovery system further includes, in fluid communication        with the Claus sulfur recovery system, a liquid-phase catalytic        oxidation sulfur recovery system    -   14. The apparatus of embodiment 1 further comprising a        regulatory system that is in fluid communication with, and        upstream from, the ammonia desulfurization system.    -   15. The apparatus of embodiment 14 wherein the regulatory system        includes a temperature regulator configured to regulate a gas        temperature in the regulatory system.    -   16. The apparatus of embodiment 15 wherein the regulatory system        includes a humidity regulator configured to regulate a gas        humidity in the regulatory system.    -   17. The apparatus of embodiment 14 wherein the regulatory system        includes a humidity regulator configured to regulate a gas        humidity in the regulatory system.    -   18. The apparatus of any of embodiments 14 to 17 further        comprising a sulfur removal device in fluid communication with        the ammonia desulfurization system    -   19. The apparatus of any of embodiments 14 to 17 further        comprising a dust removal apparatus in fluid communication with        the ammonia desulfurization system.    -   20. The apparatus of any of embodiments 14 to 17 further        comprising an impurity removal apparatus in fluid communication        with the ammonia desulfurization system.    -   21. The apparatus of any of embodiments 14 to 17 further        comprising:    -   a sulfur removal device in fluid communication with the ammonia        desulfurization system; and    -   a dust removal apparatus in fluid communication with the ammonia        desulfurization system.    -   22. The apparatus of any of embodiments 14 to 17 further        comprising:    -   a sulfur removal device in fluid communication with the ammonia        desulfurization system; and    -   an impurity removal apparatus in fluid communication with the        ammonia desulfurization system.    -   23. The apparatus of any of embodiments 14 to 17 further        comprising:    -   a dust removal apparatus in fluid communication with the ammonia        desulfurization system; and    -   an impurity removal apparatus in fluid communication with the        ammonia desulfurization system.    -   24. The apparatus of any of embodiments 18 to 23 wherein:    -   the acid gas pre-treatment system;    -   the regulatory system; and    -   the ammonia desulfurization system are connected successively        along a downstream direction.    -   25. The apparatus of embodiment 24 wherein the acid gas        pre-treatment system includes a sulfur recovery system plus        incineration system.    -   26. The apparatus of embodiment 1 further comprising a        regulatory system that is in fluid communication with, and        upstream from, the ammonia desulfurization system.    -   27. The apparatus of embodiment 26 wherein the regulatory system        includes a temperature regulator configured to regulate a gas        temperature in the regulatory system.    -   28. The apparatus of embodiment 27 wherein the regulatory system        includes a humidity regulator configured to regulate a gas        humidity in the regulatory system.    -   29. The apparatus of embodiment 28 further comprising a sulfur        removal device in fluid communication with the ammonia        desulfurization system.    -   30. The apparatus of embodiment 29 wherein:    -   the acid gas pre-treatment system;    -   the regulatory system; and    -   the ammonia desulfurization system are connected successively        along a downstream direction.    -   31. The apparatus of embodiment 30 wherein the acid gas        pre-treatment system includes a sulfur recovery system plus        incineration system.    -   32. The apparatus of embodiment 31 wherein, in the regulatory        system, the temperature regulator, humidity regulator and a the        sulfur removal device are connected successively in the        downstream direction.    -   33. The apparatus of embodiment 30 wherein, in the regulatory        system, the temperature regulator, humidity regulator and a the        sulfur removal device are connected successively in the        downstream direction.    -   34. The apparatus of embodiment 1 wherein the ammonia        desulfurization system: is configured to circulate        ammonia-containing absorption liquid; and    -   includes an absorption liquid treatment system that includes:        -   a concentration device configured to receive the absorption            liquid;        -   a solid-liquid separation device configured to collect            solids suspended in the liquid; and        -   a drying device configured to dry the collected solids.    -   35. The apparatus of embodiment 34 wherein the absorption liquid        treatment system further includes a solution purification device        in fluid communication with, and disposed in a direction        operationally downstream from, the solid-liquid separation        device.    -   36. The apparatus of embodiment 35 wherein the absorption liquid        treatment system further includes an evaporation crystallization        device that is:    -   in fluid communication with:        -   the concentration device; and        -   the solid-liquid separation device; and    -   disposed, operationally:        -   downstream from the concentration device; and        -   upstream from the solid-liquid separation device.    -   37. The apparatus of embodiment 34 wherein the absorption liquid        treatment system further includes an evaporation crystallization        device that is:    -   in fluid communication with:        -   the concentration device; and        -   the solid-liquid separation device; and    -   disposed, operationally:        -   downstream from the concentration device; and        -   upstream from the solid-liquid separation device.    -   38. The apparatus of any of embodiments 35 to 36 wherein the        solution purification device includes an oil removal device that        is in fluid communication with the solid-liquid separation        device.    -   39. The apparatus of embodiment 38 wherein the solution        purification device includes a suspended matter removal device        that is in fluid communication with the solid-liquid separation        device.    -   40. The apparatus of any of embodiments 35 to 36 wherein the        solution purification device includes a suspended matter removal        device that is in fluid communication with the solid-liquid        separation device.    -   41. The apparatus of any of embodiments 39 to 40 wherein the        suspended matter removal device is configured to provide a        circulating absorption liquid that has a suspended matter        content no greater than 200 mg/L.    -   42. The apparatus of embodiment 41 wherein the suspended matter        content is in the range 20-100 mg/L.    -   43. The apparatus of embodiment 42 wherein the suspended matter        content is in the range 30-50 mg/L.    -   44. The apparatus of embodiment 38 wherein the oil removal        device includes, in fluid communication with the solid-liquid        separation device, an air flotation device.    -   45. The apparatus of embodiment 44 wherein the oil removal        device further includes, in fluid communication with the        solid-liquid separation device, an adsorption device.    -   46. The apparatus of embodiment 45 wherein the oil removal        device further includes, in fluid communication with the        solid-liquid separation device, a precision filtration device.    -   47. The apparatus of embodiment 38 wherein the oil removal        device further includes, in fluid communication with the        solid-liquid separation device, an adsorption device.    -   48. The apparatus of embodiment 38 wherein the oil removal        device further includes, in fluid communication with the        solid-liquid separation device, a precision filtration device.    -   49. The apparatus of embodiment 47 wherein the oil removal        device further includes, in fluid communication with the        solid-liquid separation device, a precision filtration device.    -   50. The apparatus of embodiment 44 wherein the oil removal        device further includes, in fluid communication with the        solid-liquid separation device, a precision filtration device.    -   51. The apparatus of any of embodiments 44 to 50 wherein the oil        removal device is configured to produce a circulating absorption        liquid having an oil content no greater than 100 mg/L.    -   52. The apparatus of embodiment 51 wherein the oil content is in        the range 10-80 mg/L.    -   53. The apparatus of embodiment 52 wherein the oil content is in        the range 20-30 mg/L.    -   54. The device of any one of embodiments 44 to 53 wherein the        oil removal device is in fluid communication with, and is        disposed operationally upstream from, the incineration system.    -   55. A method for treating acid gas, the method comprising:    -   receiving acid gas; and    -   deriving from the acid gas:        -   ammonium sulfate; and        -   net tail gas that meets a discharge standard.    -   56. The method of embodiment 55 wherein the discharge standard        is defined in the document entitled, “Emission Standard of        Pollutants for Petroleum Refining Industry,” published as China,        GB31570-2015.    -   57. The method of embodiment 55 wherein the discharge standard        is defined in the document entitled, “Emission Standard of        Pollutants for Petroleum Chemistry Industry,” published as        China, GB31571-2015.    -   58. The method of embodiment 55 wherein the deriving includes:    -   recovering sulfur from the acid gas to produce sulfur-recovered        tail gas; and, then,    -   incinerating the sulfur-recovered gas.    -   59. The method of embodiment 55 wherein the deriving includes        producing sulfuric acid from the acid gas.    -   60. The method of embodiment 55 wherein the deriving includes        incinerating.    -   61. The method of any of embodiments 55 to 60 further comprising        channeling the acid gas from a petrochemical chemical reaction.    -   62. The method of any of embodiments 55 to 60 further comprising        channeling the acid gas from a natural gas chemical reaction.    -   63. The method of any of embodiments 55 to 60 further comprising        channeling the acid gas from a coal chemical reaction.    -   64. The method embodiment 55 wherein:    -   the deriving includes generating catalytic cracking regeneration        flue gas; and    -   the acid tail gas includes the regeneration flue gas.    -   65. The method of any of embodiments 55 to 64 wherein the        deriving comprises adjusting an enthalpy value of acid tail gas.    -   66. The method of embodiment 55 wherein the deriving includes        passing adjusted tail gas through:    -   a cooling stage,    -   an absorption stage, and    -   a water-washing stage,    -   all in an ammonia circulation desulfurization reactor.    -   67. The method of embodiment 65 wherein the adjusting includes        changing a temperature of the acid tail gas.    -   68. The method of embodiment 65 wherein the adjusting includes        changing a humidity of the acid tail gas.    -   69. The method of embodiment 68 wherein the adjusting further        includes changing a temperature of the acid tail gas.    -   70. The method of any of embodiments 67 to 69 wherein the        adjusting further includes removing sulfur from the acid tail        gas.    -   71. The method of any of embodiments 67 to 69 wherein the        adjusting further includes removing dust from the acid tail gas.    -   72. The method of any of embodiments 67 to 69 wherein the        adjusting further includes removing an impurity from the acid        tail gas.    -   73. The method of embodiment 70 wherein the adjusting further        includes removing an impurity from the acid tail gas.    -   74. The method of embodiment 71 wherein the adjusting further        includes removing an impurity from the acid tail gas.    -   75. The method of embodiment 65 wherein the adjusting adjusts        the value to 60-850 kJ/kg dry gas.    -   76. The method of embodiment 75 wherein the adjusting adjusts        the value to 80-680 kJ/kg dry gas.    -   77. The method of embodiment 76 wherein the adjusting adjusts        the value to 100-450 kJ/kg dry gas.    -   78. The method of embodiment 55 wherein the recovering includes        flowing the acid gas through a Claus sulfur recovery system        having 1 stage.    -   79. The method of embodiment 55 wherein the recovering includes        flowing the acid gas through a Claus sulfur recovery system        having 2 stages.    -   80. The method of embodiment 55 wherein the recovering includes        flowing the acid gas through a Claus sulfur recovery system        having 3 stages.    -   81. The method of embodiment 55 wherein the recovering includes        flowing the acid gas through a liquid-phase catalytic oxidation        sulfur recovery system    -   82. The method of embodiment 55 wherein the recovering includes        flowing the acid gas through a biological sulfur recovery        system.    -   83. The method of any of embodiments 78 to 80 wherein the        recovering further includes flowing the acid gas through a        SuperClaus sulfur recovery system.    -   84. The method of any of embodiments 78 to 80 wherein the        recovering further includes flowing the acid gas through a        EuroClaus sulfur recovery system.    -   85. The method of any of embodiments 78 to 80 wherein the        recovering further includes flowing the acid gas through a        biological sulfur recovery system.    -   86. The method of any of embodiments 78 to 80 wherein the        recovering further includes flowing the acid gas through a        liquid-phase catalytic oxidation sulfur recovery system.    -   87. The method of embodiment 59 wherein the sulfuric acid        production includes wet sulfuric acid production.    -   88. The method of embodiment 59 wherein the sulfuric acid        production includes dry sulfuric acid production.    -   89. The method of any of embodiments 78 to 88 wherein the        recovering includes producing sulfur-recovered gas having a        molar ratio H₂S/SO₂ in the range 1.2-3.    -   90. The method of embodiment 89 wherein the molar ratio is in        the range 1.5-2.5.    -   91. The method of embodiment 56 wherein the incinerating:    -   is performed at a temperature in the range 600° C.-1,300° C.;        and    -   produces an acid tail gas.    -   92. The method of embodiment 91 wherein, in the incinerating,        the sulfur-recovered tail gas has a residence time in the range        1 to 6 s.    -   93. The method of any of embodiments 91 to 92 wherein the acid        tail gas has an oxygen content in the range 2%-5%.    -   94. The method of any of embodiments 91 to 93 wherein the acid        tail gas has a sulfur oxide content in the range 2,000 mg/Nm³ to        150,000 mg/Nm³.    -   95. The method of any of embodiments 91 to 94 wherein the        incinerating is performed at a temperature in the range 650° C.        to 950° C.    -   96. The method of any of embodiments 91 to 95 wherein, in the        incinerating, the sulfur-recovered tail gas has a residence time        in the range 1.5 to 4 s.    -   97. The method of any of embodiments 91 to 96 wherein the acid        tail gas has an oxygen content in the range 3%-4%.    -   98. The method of any of embodiments 91 to 97 wherein the acid        tail gas has a sulfur oxide content in the range 5,000 mg/Nm³ to        55,000 mg/Nm³.    -   99. The method of embodiment 56 further comprising producing an        acid tail gas having a sulfur oxide content in the range 2,000        mg/Nm³ to 150,000 mg/Nm³.    -   100. The method of embodiment 99 wherein the incinerating:    -   is performed at a temperature in the range 600° C.-1,300° C.;        and    -   produces the acid tail gas.    -   101. The method of any of embodiments 99 to 100 further        comprising incinerating sulfur-recovered tail gas having an        incineration residence time in the range 1 to 6 s.    -   102. The method of any of embodiments 99 to 101 wherein the acid        tail gas has an oxygen content in the range 2%-5%.    -   103. The method of any of embodiments 99 to 102 wherein the        incinerating is performed at a temperature in the range 650° C.        to 950° C.    -   104. The method of any of embodiments 99 to 103 wherein, in the        incinerating, the sulfur-recovered tail gas has a residence time        in the range 1.5 to 4 s.    -   105. The method of any of embodiments 99 to 104 wherein the acid        tail gas has an oxygen content in the range 3%-4%.    -   106. The method of any of embodiments 99 to 105 wherein the acid        tail gas has a sulfur oxide content in the range 5,000 mg/Nm³ to        55,000 mg/Nm³. 107. The method of embodiment 56 further        comprising producing an acid tail gas having an oxygen content        in the range 2%-5%.    -   108. The method of embodiment 107 wherein the acid tail gas has        a sulfur oxide content in the range 2,000 mg/Nm³ to 150,000        mg/Nm³.    -   109. The method of any of embodiments 107 to 108 wherein the        incinerating:    -   is performed at a temperature in the range 600° C.-1,300° C.;        and    -   produces the acid tail gas.    -   110. The method of any of embodiments 107 to 109 wherein, in the        incinerating, the sulfur-recovered tail gas has a residence time        in the range 1 to 6 s.    -   111. The method of any of embodiments 107 to 110 wherein the        incinerating is performed at a temperature in the range 650° C.        to 950° C.    -   112. The method of any of embodiments 107 to 111 wherein, in the        incinerating, the sulfur-recovered tail gas has a residence time        in the range 1.5 to 4 s.    -   113. The method of any of embodiments 107 to 112 wherein the        acid tail gas has an oxygen content in the range 3%-4%.    -   114. The method of any of embodiments 107 to 113 wherein the        acid tail gas has a sulfur oxide content in the range 5,000        mg/Nm³ to 55,000 mg/Nm³.    -   115. The method of embodiment 56 wherein, in the incinerating,        the sulfur-recovered tail gas has a residence time in the range        1 to 6 s.    -   116. The method of any of embodiment 115 further comprising        producing acid tail gas having an oxygen content in the range        2%-5%.    -   117. The method of any of embodiments 115 to 116 further        comprising producing acid tail having a sulfur oxide content in        the range 2,000 mg/Nm³ to 150,000 mg/Nm³.    -   118. The method of any of embodiments 115 to 117 wherein the        incinerating:    -   is performed at a temperature in the range 600° C.-1,300° C.;        and    -   produces an acid tail gas.    -   119. The method of any of embodiments 115 to 118 wherein the        incinerating is performed at a temperature in the range 650° C.        to 950° C.    -   120. The method of any of embodiments 115 to 119 wherein, in the        incinerating, the sulfur-recovered tail gas has a residence time        in the range 1.5 to 4 s.    -   121. The method of any of embodiments 115 to 120 wherein the        acid tail gas has an oxygen content in the range 3%-4%.    -   122. The method of any of embodiments 115 to 121 wherein the        acid tail gas has a sulfur oxide content in the range 5,000        mg/Nm³ to 55,000 mg/Nm³.    -   123. The method of embodiment 55 wherein the deriving includes        reducing a suspended matter content of an ammonia        desulfurization circulating absorption liquid to no greater than        200 mg/L.    -   124. The method of embodiment 123 wherein the deriving further        includes reducing an oil content of an ammonia desulfurization        circulating absorption liquid to no greater than 100 mg/L.    -   125. The method of embodiment 55 wherein the deriving includes        reducing an oil content of an ammonia desulfurization        circulating absorption liquid to no greater than 100 mg/L.    -   126. The method of 67 wherein the adjusting produces adjusted        tail gas having an organic matter content not greater than 30        ppm.    -   127. The method of 67 wherein the adjusting produces adjusted        tail gas having an elementary sulfur and hydrogen sulfide        content not greater than 30 ppm.    -   128. The method of any of embodiments 126 to 127 wherein the        adjusting produces adjusted tail gas having an organic matter        content not greater than 10 ppm.    -   129. The method of any of embodiments 126 to 128 wherein the        adjusting produces adjusted tail gas having an elementary sulfur        and hydrogen sulfide content not greater than 10 ppm.    -   130. The method of 68 wherein the adjusting produces adjusted        tail gas having an elementary sulfur and hydrogen sulfide        content not greater than 30 ppm.    -   131. The method of 68 wherein the adjusting produces adjusted        tail gas having an organic matter content not greater than 30        ppm.    -   132. The method of any of embodiments 130 to 131 wherein the        adjusting produces adjusted tail gas having an organic matter        content not greater than 10 ppm.    -   133. The method of any of embodiments 130 to 132 wherein the        adjusting produces adjusted tail gas having an elementary sulfur        and hydrogen sulfide content not greater than 10 ppm.    -   134. The method of any one of the preceding embodiments wherein        the specific process steps include:    -   a) acid gas is treated by sulfur recovery plus incineration or        sulfuric acid production or incineration, or directly by        catalytic cracking catalyst regeneration process to obtain acid        tail gas;    -   b) the acid tail gas is fed into the regulatory system to adjust        the enthalpy value of the tail gas to be within the range of        60-850 kJ/kg dry gas, for example 80-680 kJ/kg dry gas or        100-450 kJ/kg dry gas;    -   c) the acid tail gas which meets the enthalpy value requirement        is fed into the ammonia desulfurization process for treatment,        to achieve the purpose that net tail gas meets the discharge        standard through multi-stage circulating absorption.

Thus, apparatus and methods for treating acid gas have been provided.Persons skilled in the art will appreciate that the present inventioncan be practiced by other than the described examples, which arepresented for purposes of illustration rather than of limitation. Thepresent invention is limited only by the claims that follow.

1-54. (canceled)
 55. A method for treating acid gas, the methodcomprising: receiving acid gas having an elementary sulfur and hydrogensulfide content that is not greater than 30 ppm; regulating an enthalpyvalue of the acid gas to 66-850 kJ/kg dry acid gas; and, then, derivingfrom the acid gas: ammonium sulfate; and net tail gas that has a sulfurdioxide content no greater than 400 mg/m³. 56-57. (canceled)
 58. Themethod of claim 55 wherein the deriving includes: recovering sulfur fromthe acid gas to produce sulfur-recovered tail gas; and, then,incinerating the sulfur-recovered tail gas.
 59. The method of claim 55wherein the deriving includes producing sulfuric acid from the acid gas.60. The method of claim 55 wherein the deriving includes incinerating.61. The method of claim 55 further comprising channeling the acid gasfrom a petrochemical chemical reaction.
 62. The method of claim 55further comprising channeling the acid gas from a natural gas chemicalreaction.
 63. The method of claim 55 further comprising channeling theacid gas from a coal chemical reaction.
 64. The method of claim 55wherein: the deriving includes generating catalytic crackingregeneration flue gas; and the acid gas includes the catalytic crackingregeneration flue gas.
 65. The method of claim 55 wherein the derivingcomprises adjusting an enthalpy value of acid gas.
 66. The method ofclaim 55 wherein the deriving includes passing adjusted tail gas formedin the regulatory system through: a cooling stage, an absorption stage,and a water-washing stage, all in an ammonia circulation desulfurizationreactor.
 67. The method of claim 65 wherein the adjusting includeschanging a temperature of the acid gas.
 68. The method of claim 65wherein the adjusting includes changing a humidity of the acid gas. 69.The method of claim 68 wherein the adjusting further includes changing atemperature of the acid gas. 70-133. (canceled)
 134. The method of claim58 further comprising channeling the acid gas from a petrochemicalchemical reaction.
 135. The method of claim 59 further comprisingchanneling the acid gas from a petrochemical chemical reaction.
 136. Themethod of claim 60 further comprising channeling the acid gas from apetrochemical chemical reaction.
 137. The method of claim 58 furthercomprising channeling the acid gas from a natural gas chemical reaction.138. The method of claim 59 further comprising channeling the acid gasfrom a natural gas chemical reaction.
 139. The method of claim 60further comprising channeling the acid gas from a natural gas chemicalreaction.
 140. The method of claim 58 further comprising channeling theacid gas from a coal chemical reaction.
 141. The method of claim 59further comprising channeling the acid gas from a coal chemicalreaction.
 142. The method of claim 60 further comprising channeling theacid gas from a coal chemical reaction.
 143. The method of claim 58wherein the deriving comprises adjusting an enthalpy value of acid gas.144. The method of claim 143 wherein the adjusting includes changing atemperature of the acid gas.
 145. The method of claim 143 wherein theadjusting includes changing a humidity of the acid gas.
 146. The methodof claim 145 wherein the adjusting further includes changing atemperature of the acid gas.
 147. The method of claim 59 wherein thederiving comprises adjusting an enthalpy value of acid gas.
 148. Themethod of claim 147 wherein the adjusting includes changing atemperature of the acid gas.
 149. The method of claim 147 wherein theadjusting includes changing a humidity of the acid gas.
 150. The methodof claim 149 wherein the adjusting further includes changing atemperature of the acid gas.